Spacers for insulating glass panes generally comprise hollow profile rods that are made of aluminum or stainless steel containing a pourable desiccant, typically molecular sieves. The aim of the desiccant is to bind moisture present in the insulating glass pane, so that the dew point is always met in the insulating glass pane at the temperatures that occur. Metallic spacers are today generally bent in one piece from a hollow profile rod, into which the desiccant has already been filled. Prior to bending a corner, the inside wall is notched, so that the corner forms precisely at the intended site and has a defined appearance. The inside wall shall be understood as the wall of the spacer facing the inside of the insulating glass pane. The all of the hollow profile rod located opposite of the inside wall is referred to as the outside wall or base. The two walls connecting the inside wall and outside wall to each other and facing the individual glass plates inside the insulating glass pane are referred to as the flanks; they typically run predominantly parallel to each other because they have to be glued to the glass plates. At the flanks, during bending the hollow profile rod tends to arch outward and/or form outwardly protruding pleats. In an effort to prevent this, the hollow profile rods are clamped at the flanks between jaws, which force the hollow profile rods not to widen in a corner during bending, see EP 1 281 451 A1.
After bending, the two mutually opposing ends of the hollow profile rod are joined by way of a connector and a closed frame is formed thereby. The hollow profile rods to be bent are generally connected consecutively to each other by straight connectors. The spacers may therefore also comprise a plurality of straight connectors. Such frame-shaped metallic spacers are characterized by good mechanical stability. However, they have the disadvantage that the production thereof is complex.
Furthermore, spacer frames are known that are made of metallic U-profiles, thermoplastic solid profiles, which are extruded directly onto a glass plate, and plastic hollow profiles, which like the spacers made of metallic hollow profile rods can be filled with a granular, pourable desiccant.
Spacers made of plastic hollow profiles have only low thermal conductivity, so that they impair the heat transfer between the individual glass plates of the insulating glass pane in the desirable manner. The disadvantage, however, is that hollow profile rods made of plastic cannot be bent to form squared frames, when they have the hardness and strength required for the use as spacers in insulating glass panes. This applies in particular to hollow profile rods made of glass fiber reinforced plastic. One might consider to form spacer frames from plastic hollow profiles in that straight hollow profile sections, which form the sides of the frame-shaped spacers, are connected to each other by inserting angle pieces made of metal into the corners of the hollow profile sections, where they engage with barbs. This technology known from earlier times for the production of metallic spacers, however, is labor-intensive and results in spacer frames which as a result of a lack of rigidity are overall unstable in the corner region and cannot be easily handled and glued to a glass plate with the necessary precision. In addition, spacer frames comprising such inserted corners are unfavorable in light of the fact that insulating glass panes must be hermetically sealed at the edge thereof to prevent the penetration of moisture.
It is furthermore known to form spacers from metallic hollow rod profiles by connecting individual hollow profile rods at the corners of the spacers by angle pieces, which have two sides that are connected by a hinge and can be latched to each other in a position in which the sides include a right angle with each other. For this purpose, the individual hollow profile rods are first connected to each other in a straight line, provided at the flanks thereof continuously with an adhesive sealant, and then formed into a frame by pivoting the hollow profile rods about the hinge of the respective angle piece, said frame being close by a linear connector that is inserted in the corners of the hollow profile rod. Such a configuration of the corners results in unstable spacers having the disadvantages described above.
In order to produce spacers from plastic hollow profile rods in one piece, it is already known from EP 0 947 659 A2 and EP 1 030 024 A2 to disengage the hollow profile rods at the sites where corners are to be formed by producing V-shaped notches, the tips of which extend to the wall of the hollow profile strip located on the outside in the finished spacer. So as to shape a frame, only the outside wall of the hollow profile rod is bent at the disengaged sites thereof. While in this way spacers are obtained, which also have a closed outside wall at the corners, the frame is an unstable structure and requires stabilization because the sides of the spacer at the corners only adhere to each other by the outside wall thereof. For this purpose, it is known from EP 0 947 659 A2 and EP 1 030 024 A2 to mold a thermoplastic resin in the corner regions of the spacer frame through an open in one of the flanks thereof, wherein the resin bridges the corners and lends the spacer the necessary stability after the plastic has cooled and cured. The disadvantage is that it takes comparatively long until the plastic has cooled off and solidified. In order to shorten the time, it is known from EP 1 030 024 A2 to transfer the spacer during production, after injecting the plastic, in a special curing zone, while maintaining the angle of the bent corner. This method is time-intensive and costly.
In contrast, significant progress was provided by WO 2006/077096 A1, which discloses a spacer for insulating glass panes which is produced from a hollow profile rod made of plastic by providing it at the sites intended for the corners with a recess, which opens the inside wall and the two flanks of the hollow profile wall, but leaves the outside wall intact. In order to stabilize the corners, angle pieces are used, which have two sides connected by a hinge and can be transferred from a rectilinear shape into an angled shape, in which they can be fixed relative to each other. Such an angle piece is initially positioned in a rectilinear fashion in the region of the respective corner that is to be formed. The corner is then formed by bending the hollow profile rod and it is stabilized by the sides of the angle piece that latch to each other in the specified angular position. It is furthermore known from WO 2006/007096 A1 to apply an adhesive sealant and a desiccant-containing compound to the hollow profile rod, which is still in the rectilinear state and in which the angular pieces, which are still in the rectilinear state, have already been inserted, then to form the corners in the hollow profile rod, and to glue the corners of the hollow profile rod to each other.